Some earth moving machines, for example dozers, motor graders, and snow plows, have a front-mounted work tool such as a blade, bucket, or plow for pushing, carrying, and/or dumping material. These work tools can be tilted and pitched by paired cylinders located to either side of the work tool. Tilting may be accomplished by extending and retracting a single cylinder or extending one cylinder while retracting the other cylinder. Pitching can be separately accomplished by extending or retracting both cylinders in the same direction at the same time.
As a machine of this type operates, an operator and/or an automatic blade control system may tilt the work tool in one or more directions to perform one or more operations, such as to move material and/or steer the machine. In some instances, however, extension and retraction of one or more of the paired cylinders during a tilt operation may inadvertently change the pitch of the work tool. For example, left and right tilting of a dozer blade during a steering operation may gradually cause the blade to pitch outwardly, resulting in a more aggressive cutting edge angle. If the resulting work tool pitch is not adjusted, subsequent operation of the machine may be inefficient. If an operator recognizes that the pitch of the work tool is incorrect, the operator may have to manually adjust the pitch, complicating control of the machine and interrupting an operation that was being performed.
One example of a control system for adjusting the pitch of a work tool is disclosed in U.S. Pat. No. 5,862,868, which issued to Yamamoto et al. on Jan. 26, 1999 (“the '868 patent”). In particular, the '868 patent discloses a control system that automatically resets a bulldozer blade to a predetermined excavating pitch while the bulldozer is traveling backwardly, after it has completed an operation of excavating, carrying, or dumping earth. While the control system of the '868 patent may simplify control of a bulldozer blade, it does not address the problems caused by an inadvertent change in blade pitch. That is, even if a work tool (such as the bulldozer blade of the '868 patent) is automatically reset to a particular pitch when a machine has finished an operation (such as when the machine travels backwardly), any inadvertent changes in work tool pitch may have already had an effect and caused inefficient operation of the machine.
The present disclosure is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.